Piston construction



Oct. 20, 1925.

L. M. STELLMANN PISTON CONSTRUCTION Filed A 2 Sheets-Sheet 1 Pril 18 1922 Oct- 20; 1925- L. STELLMANN PISTON CONSTRUCTION Filed April 18, 1922 2 Shoals-Sheet 2 YNVENTOR.

BY 2 ATTORNEYS.

[TED STATES PATENT OFFICE. '7

LOUIS M. STELLMANN, OF SYRACUSE, NEW YORK, ASSIGNORYTO H. H. FRANKLIN MANU- FACTURING COMPANY, OF SYRACUSE, NEW YORK, A CORPORATION OF NEW YORK.

, PISTON CONSTRUCTION.

Application filed April 18, 1922. Serial no. 554,748.

To all whom it may concern:

Be it known that T, LOUIS M. STELLMANn,

a and State of New York, have invented a certain new and useful Piston Construction, of which the following is a specification.

This invention relates to pistons more particularly for internal combustion engines, which pistons are formed of a metal as aluminum alloy, having a greater coefficient of expansion than the cylinder walls which are usually'of cast iron; and has for its object an expansible piston having a portion of its skirt or sleeve filling and conforming to the cylinder at all temperatures of the engines and other portions of its sleeve or skirt normally spaced apart from the cylinder walls and movable or expansible outwardly toward the cylinder walls to conform to the curve thereof, as the piston expands under the influence of the heat generated in the operation of the engine, the expansible portions carrying. the wrist pin bosses and constituting approximately twothirds of the cylinder.

The invention consists in the novel features, and in the combinations and con structions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

Figure 1 is a fragmentary vertical sectional view of this piston, the contiguous portion of the cylinder and also the wrist pin and connecting rod and other parts of the engine being also shown, the connecting rod being broken away at one end.

Figure 2 is a sectional view of the piston similar to that shown in Fig. 1, the cylinder.

and other parts of the engine being omitted. Figure 3 is a sectional view of the piston taken at a right angle to Fig. 2.

Figure 4 is an elevation of the piston. Figure 5 is a transverse sectional view through the piston on line 4-4, Fig. 2.

Figure 6 is a diagrammatic view illustrating the position of the piston in the cylinder, the eccentric or expansible portions or walls of the piston being exaggerated to clearly illustrate the operation or expansion of the piston relatively to the cylinder.

Figure 7 is a detail view of the ring for holding the wrist pins from displacement.

This piston comprises a head portion provided with the usual grooves for the piston rings, and a sleeve. the sleeve having diametrically opposite eccentric expansible portions extending in arcs of greater radius than the normal radius or the radius of diametrically opposite concentric portions of the piston arranged between the expansible portions.

The concentric portions are arranged on the bearing or thrust sides of the piston and are of considerably less width than the eccentric portions, and the pin bosses are car-f ried by the eccentric expansible portions.

1 designates the piston having a head 2 provided with the usual grooves 3 for the piston rings 4:.

5 is the sleeve of the piston which is connected to the head by diametrically opposite integral portions at 7 and also by internal brackets or webs8, the connecting portions 7 and webs 8 being located above the pin bosses 9.

The sleeve is also separated from the head by slots 10 located on diametrically opposite sides thereof on opposite sides of the connecting portions 7 and webs 8.

The sleeve 5 is automatically expansible to fit the cylinder and has concentric portions 11 on diametrically opposite sides thereof which slidably fit the bore of the cylinder and other diametrically opposite eccentric portions 12 between arcs of greater radius than the radius of the concentric portions and the center of the arc of each eccentric portion being located at 12 on the opposite side of the longitudinal axis 13 of the piston from that on which the eccentric portion 12 is located.

In the interest of brevity,-the piston thus may be considered to be slightly elleptical in general form in cross section although it is not a true ellipse as its ends are concentric with the axis of the piston andthe outline of the piston is not a true ellipse.

The concentric portions 11 are a ranged on the bearing or thrust sides of the piston and each constitutes approximately one-sixth of the sleeve, and the wrist pin bosses 9' project inwardly from the intermediate portions of the eccentric sides of the piston, each of which constitute approximately one-third of the sleeve.

The outer faces of the sleeve are slightly tapered toward the lower endof the piston as indicated in Fig. 5.

Preferably, the concentric portions 11 of the piston are formed with lengthwise slots 11 opening through the lower end of the piston and extending to a point above the axis of the pin bosses.

The piston is shown as provided with peripheral recesses 14 on diametrically opposite sides thereof in the connecting portion 7 in line with the slots 10. These recesses perform no function in the use of the piston but are present for manufacturing purposes for the purpose of facilitating the cutting of the slots 10 by turning operation.

, portions on walls 12 of the sleeve and hence I The slots 10 entirely separate the concentric endportions or walls of the sleeve from the head and partly separate portions of the eccentric walls on opposite sides of the connecting neck 7 from the head.

The wrist pin bosses 9 as before stated, are carried by the eccentric or expansible move radially during the expansion of such ,walls, and the wrist pin 15 is slidably orv fioatingly mounted in the wrist pin bosses and it is also preferably slidingly or floatingly mounted in the bearing 16 of the connecting rod 17.

In order to prevent the wrist pin from sliding into engagement with the cylinder walls and scoring the cylinder, the piston is provided with means for holding the pin from axial displacement beyond the periphery of the piston.

In the illustrated embodiment of my ,invention, the sleeve is formed with a circumferential groove 18 which extends across the outer ends of the wrist pin bosses, and a retaining ring 19 is seated in the groove and thus prevents outward movement of the wrist pin.

In case the piston pin becomes broken in use the ring 19 holds the fragment thereof from dropping down into the engine base and damaging other parts of the engine.

In operation, the piston is placed in the cylinder with the concentric portions 11 fitting the bore of the cylinder and holding the piston from slapping. As the piston becomes heated, the eccentric portions 12 thereof expand or bow outwardly toward or into continuations of the arcs of the concentric portions 11 and relieve undue tightness between the concentric portions 11 and' the cylinder walls.

his piston construction is particularly advantageous in pistons made of aluminum or aluminum alloy or some metal having a greater coefficient of expansion than the cylinder, in that the piston is made to fit the cylinder at all temperatures of the engine, without relying upon resiliency of the metal. Hence, the liability of a resilient metal taking a permanent set is eliminated as in compressible pistons which sooner or later take a permanent set, and become sloppy.

What I claim is.

1. A piston for internal combustion engines comprising a head and a sleeve, the sleeve beingslightly elliptical in general form in cross section, and the sleeve being formed with longitudinal slots arranged in the end walls of the elliptical form, the sleeve having pin bosses extending inwardly from the long walls of the elliptical form along a short diameter of the eliptical form and each of the long walls of the ellipse being approximately one third of the sleeve, substantially as and for the purpose specified.

2. A piston for internal combustion engines comprising a head, and a sleeve, the sleeve having diametrically opposite portions of its wall of equal width concentric with the axis of the piston and other diametrically opposite eccentric expansible portions between the concentric portions having their outer faces of greater radius than the concentric portions and located within continuations of the arcs of the outer faces of the concentric portions, each eccentric portion constituting approximate- 1y one-third of the sleeve, the concentric portions being formed with lengthwise slots opening through the lower end of the sleeve, and pin bosses projecting inwardly from the eccentric portions substantially midway between the concentric portions, substantially as and for the purpose specified.

3. A piston for internal combustion en gines, comprising a head, and a sleeve, the sleeve havlng diametrically opposite portions'of its wall of equal width concentric with the axis of the piston and other diametrically opposite eccentric expansible portions between the concentric portions, the eccentric portions having their outer faces of greater radius than the concentric portions and located within continuations of the arcs of the outer faces of the concentric portions, each eccentric portion constituting approximately one-third of the sleeve, the concentric portions being formed with lengthwise slots opening through the lower end of the sleeve, and pin bosses projecting inwardly from the eccentric portions substantially midway between the concentric portions, the slots being located in the portion of the sleeve at the end of the ellipse approximately midway between the pin bosses.

4. A piston for internal combustion en-.

gines having a head and a sleeve, transverse slots in diametrically opposite sides of the piston separating the opposite side portions of the head from the sleeve, whereby the head is connected to the sleeve between the ends of the slots, the sleeve being slightly elliptical in general form in cross section, the ends of the elliptical form being concentric with the axis of the piston, and wrist pin bosses projecting from the portions of the sleeve joined to the head between the ends of the slots, the axis of said pin bosses extending along the short diameter of the elliptical form, substantially as and for the purpose specified.

5. A piston for internal combustion engines having a head and a sleeve, transverse slots in diametrically opposite sides of the piston separating the opposite side portions of the head from the sleeve, whereby the head is connected to the sleeve between the ends of the slots, the sleeve being slightly elliptical in general form in cross section, the ends of the elliptical form bein concentric with the axis of the piston, and wrist pin bosses projecting from the portions of the sleeve joined to the head between the ends of the slots, the axis of said pin bosses extending along the short diameter of the elliptical form, the sleeves being also formed with lengthwise slots midway between the ends of the transverse slots, substantially as and for the purpose set forth.

In testimony whereof, I have hereunto signed my name, at Syracuse, in the county of Onondaga, and State of New York, this day of February, 1922.

LOUIS. M. STELLMANN. 

